#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************




vector<int> a;
vector<int> b;

int kadane(vector<int>& a, int n){
    int maxi = INT32_MIN;
    int last = 0;
    for(int i=0; i<n; i++){
        int curr = max(a[i], last+a[i]);
        last = curr;
        maxi = max(maxi, curr);
    }
    return maxi;
}


int consistency(int n){
	
    vector<int> ab(n);
    
    int suma = 0;
    for(int i=0; i<n; i++){
        suma += a[i];
        ab[i] = a[i]-b[i];
    }
    
    vector<int> ba(n);
    
    int sumb = 0;
    for(int i=0; i<n; i++){
        sumb += b[i];
        ba[i] = b[i]-a[i];
    }
    
    int sum1 = kadane(ab, n);
    int sum2 = kadane(ba, n);
    
    return max(sumb+sum1, suma+sum2);

}















int practice(int n){


    return 0;
}





void solve() {
    
    int n;
    cin>> n;
    
    a.resize(n);
    b.resize(n);
    for(int i=0; i<n; i++) cin >> a[i];
    for(int i=0; i<n; i++) cin >> b[i];
    
    cout << consistency(n) << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}